Remote vs. local ischaemic preconditioning in the rat heart: infarct limitation, suppression of ischaemic arrhythmia and the role of reactive oxygen species

Alleviating hypoxia and oxidative stress for treatment of cardiovascular diseases: a biomaterials perspective

A state of hypoxia (lack of oxygen) persists in the initial and later phases of healing in cardiovascular diseases, which can alter the tissue's repair or regeneration, ultimately affecting the structure and functionality of the related organ. Consequently, this results in a cascade of events, leading to metabolic stress and the production of reactive oxygen species (ROS) and autophagy. This unwanted situation not only limits the oxygen supply to the needy tissues but also creates an inflammatory state, limiting the exchange of nutrients and other supplements. Consequently, biomaterials have gained considerable attention to alleviate hypoxia and oxidative stress in cardiovascular diseases. Numerous oxygen releasing and antioxidant biomaterials have been developed and proven to alleviate hypoxia and oxidative stress. This review article summarizes the mechanisms involved in cardiovascular pathologies due to hypoxia and oxidative stress, as well as the treatment modalities currently in practice. The applications, benefits and possible shortcomings of these approaches have been discussed. Additionally, the review explores the role of novel biomaterials in combating the limitations of existing approaches, primarily focusing on the development of oxygen-releasing and antioxidant biomaterials for cardiac repair and regeneration. It also directs attention to various other potential applications with critical insights for further advancement in this area.

Short-Term and Long-Term Effects of Ischemic Conditioning on Liver Transplantation: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Although liver transplantation (LT) is one of the definitive treatments for patients with end-stage liver failure, it inevitably results in ischemic reperfusion injury. It is known that prognosis is improved when temporary ischemic conditioning (IC) is applied to patients with ischemic reperfusion injury. The objective of this meta-analysis was to determine the short-term and long-term effects of IC on the clinical outcomes of LT recipients.

METHODS

Randomized controlled studies on IC in patients with LTs were included. Patients were compared between an IC group and a sham group. Studies were retrieved from PubMed, Embase, and Cochrane Library. The risk of bias was evaluated using RoB 2.0. Mortality, graft function, and major complications were synthesized using RevMan 5.4.1.

RESULTS

Among 316 papers, 17 articles (1196 patients) were included. There was an insignificant increase in short-term mortality (risk ratio [RR]: 3.00, 95% CI: 0.32-28.14, P = .34). However, long-term mortality was lower in the IC group than in the sham group, but not significantly (RR: 0.75; 95% CI: 0.47-1.20, P = .23). Short-term graft function (acute graft rejection and primary graft non-function) was not improved by IC. One-year graft loss tended to show better results in the IC group (RR: 0.53, 95% CI: 0.26-1.07, P = .08).

CONCLUSION

Ischemic conditioning did not have a beneficial effect on LT. Although long-term outcomes appear to be better in the IC group than in the sham group, further randomized controlled trials are needed.

Ultra-High-Resolution Electrocardiography Enables Earlier Detection of Transmural and Subendocardial Myocardial Ischemia Compared to Conventional Electrocardiography

The sensitivity of exercise ECG is marginally sufficient for the detection of mild reduction of coronary blood flow in patients with early coronary atherosclerosis. Here, we describe the application of a new technique of ECG registration/analysis-ultra-high-resolution ECG (UHR ECG)-for early detection of myocardial ischemia (MIS). The utility of UHR ECG vs. conventional ECG (C ECG) was tested in anesthetized rats and pigs. Transmural MIS was induced in rats by the ligation of the left coronary artery (CA). In pigs, subendocardial ischemia of a variable extent was produced by stepwise inflation of a balloon within the right CA, causing a 25-100% reduction of its lumen. In rats, a reduction in power spectral density (PSD) in the high-frequency (HF) channel of UHR ECG was registered at 60 s after ischemia (power 0.81 ± 0.14 vs. 1.25 ± 0.12 mW at baseline, p < 0.01). This was not accompanied by any ST segment elevation on C ECG. In pigs, PSD in the HF channel of UHR ECG was significantly decreased at a 25% reduction of CA lumen, while the ST segment on C ECG remained unchanged. In conclusion, UHR ECG enabled earlier detection of transmural MIS compared to C ECG. PSD in the HF channel of UHR ECG demonstrated greater sensitivity in the settings of subendocardial ischemia.

Overview of Cardiac Arrhythmias and Treatment Strategies

Maintenance of normal cardiac rhythm requires coordinated activity of ion channels and transporters that allow well-ordered propagation of electrical impulses across the myocardium. Disruptions in this orderly process provoke cardiac arrhythmias that may be lethal in some patients. Risk of common acquired arrhythmias is increased markedly when structural heart disease caused by myocardial infarction (due to fibrotic scar formation) or left ventricular dysfunction is present. Genetic polymorphisms influence structure or excitability of the myocardial substrate, which increases vulnerability or risk of arrhythmias in patients. Similarly, genetic polymorphisms of drug-metabolizing enzymes give rise to distinct subgroups within the population that affect specific drug biotransformation reactions. Nonetheless, identification of triggers involved in initiation or maintenance of cardiac arrhythmias remains a major challenge. Herein, we provide an overview of knowledge regarding physiopathology of inherited and acquired cardiac arrhythmias along with a summary of treatments (pharmacologic or non-pharmacologic) used to limit their effect on morbidity and potential mortality. Improved understanding of molecular and cellular aspects of arrhythmogenesis and more epidemiologic studies (for a more accurate portrait of incidence and prevalence) are crucial for development of novel treatments and for management of cardiac arrhythmias and their consequences in patients, as their incidence is increasing worldwide.

Protective Effect of Remote Ischemic Preconditioning against Myocardial Ischemia-Reperfusion Injury in Rats and Mice: A Systematic Review and Meta-Analysis

Background

Remote ischemic preconditioning (RIPC) has cardioprotective effects. This study was designed to evaluate the effectiveness and potential influencing factors of RIPC for myocardial ischemia-reperfusion injury (MIRI) in rats and mice.

Methods

The PubMed, Web of Science, Embase, and Cochrane Library databases were searched to identify animal model studies that explored the effect of RIPC on MIRI. The primary outcome was myocardial infarct size, and secondary outcomes included serum cardiac markers, vital signs, hemodynamic parameters, and TUNEL-positive cells. Quality was assessed using SYRCLE's Risk of Bias Tool.

Results

This systematic review and meta-analysis included 713 male animals from 37 studies. RIPC significantly protected against MIRI in small animal models by reducing infarct size, decreasing serum myocardial marker levels and cell death, and improving cardiac function. Subgroup analysis indicated that RIPC duration and sites influence the protective effect of RIPC on MIRI. Meta-regression suggested that study type and staining method might be sources of heterogeneity. The funnel plot, Egger's test, and Begg's test suggested the existence of publication bias, but results of the sensitivity analysis and nonparametric trim-and-fill method showed that the overall effect of RIPC on MIRI infarct size was robust.

Conclusions

RIPC significantly protected against MIRI in small animal models by reducing infarct size, decreasing serum myocardial markers and limiting cell death, and improving cardiac function. RIPC duration and site influence the protective effect of RIPC on MIRI, which contributes in reducing confounding factors and determines the best approach for human studies.

Reactive Oxygen Species Scavenging Nanomedicine for the Treatment of Ischemic Heart Disease

Ischemic heart disease (IHD) is the leading cause of disability and mortality worldwide. Reactive oxygen species (ROS) have been shown to play key roles in the progression of diabetes, hypertension, and hypercholesterolemia, which are independent risk factors that lead to atherosclerosis and the development of IHD. Engineered biomaterial-based nanomedicines are under extensive investigation and exploration, serving as smart and multifunctional nanocarriers for synergistic therapeutic effect. Capitalizing on cell/molecule-targeting drug delivery, nanomedicines present enhanced specificity and safety with favorable pharmacokinetics and pharmacodynamics. Herein, the roles of ROS in both IHD and its risk factors are discussed, highlighting cardiovascular medications that have antioxidant properties, and summarizing the advantages, properties, and recent achievements of nanomedicines that have ROS scavenging capacity for the treatment of diabetes, hypertension, hypercholesterolemia, atherosclerosis, ischemia/reperfusion, and myocardial infarction. Finally, the current challenges of nanomedicines for ROS-scavenging treatment of IHD and possible future directions are discussed from a clinical perspective.

Impact of Maturation on Myocardial Response to Ischemia and the Effectiveness of Remote Preconditioning in Male Rats

Aging attenuates cardiac tolerance to ischemia/reperfusion (I/R) associated with defects in protective cell signaling, however, the onset of this phenotype has not been completely investigated. This study aimed to compare changes in response to I/R and the effects of remote ischemic preconditioning (RIPC) in the hearts of younger adult (3 months) and mature adult (6 months) male Wistar rats, with changes in selected proteins of protective signaling. Langendorff-perfused hearts were exposed to 30 min I/120 min R without or with prior three cycles of RIPC (pressure cuff inflation/deflation on the hind limb). Infarct size (IS), incidence of ventricular arrhythmias and recovery of contractile function (LVDP) served as the end points. In both age groups, left ventricular tissue samples were collected prior to ischemia (baseline) and after I/R, in non-RIPC controls and in RIPC groups to detect selected pro-survival proteins (Western blot). Maturation did not affect post-ischemic recovery of heart function (Left Ventricular Developed Pressure, LVDP), however, it increased IS and arrhythmogenesis accompanied by decreased levels and activity of several pro-survival proteins and by higher levels of pro-apoptotic proteins in the hearts of elder animals. RIPC reduced the occurrence of reperfusion-induced ventricular arrhythmias, IS and contractile dysfunction in younger animals, and this was preserved in the mature adults. RIPC did not increase phosphorylated protein kinase B (p-Akt)/total Akt ratio, endothelial nitric oxide synthase (eNOS) and protein kinase Cε (PKCε) prior to ischemia but only after I/R, while phosphorylated glycogen synthase kinase-3β (GSK3β) was increased (inactivated) before and after ischemia in both age groups coupled with decreased levels of pro-apoptotic markers. We assume that resistance of rat heart to I/R injury starts to already decline during maturation, and that RIPC may represent a clinically relevant cardioprotective intervention in the elder population.

Activity of ROS-induced processes in the combined preconditioning with amtizol before and after cerebral ischemia in rats

Introduction: The dose-dependent effect of reactive oxygen species (ROS) in tissues in preconditioning (PreC) and oxidative stress, as well as NO-synthase participation in mitochondrial ROS production determined the study aim – to assess the impact of the neuroprotective method of combined preconditioning (CPreC) on free radical reactions (FRRs) in brain in normoxia and in cerebral ischemia, including in NO-synthase blockade.

Materials and methods: The intensity of FRR by iron-induced chemiluminescence (CL), the content of lipid peroxidation products and antioxidant enzyme activity were investigated 1 hr (early period) and 48 hrs (delayed period) after CPreC (amtizol and hypobaric hypoxia) in Wistar rat brain. Some animal groups were operated (common carotid artery bilateral ligation) 1 hr and 48 hrs after CPreC, as well as with preliminary introduction of L-NAME and aminoguanidine.

Results and discussion: In normoxia, CPreC led to increase the CL maximum level (Fmax) in the delayed PreC period. The amount of thiobarbituric acid reactive products (TBA-RP), activity of superoxide dismutase (SOD) and catalase in mitochondrial fraction of rat brain did not change in comparison with the intact control in both PreC periods. In cerebral ischemia, oxidative stress was observed. The CPreC use before ischemia caused a decrease in CL parameters and TBA-RP in brain, the maintenance of SOD and high catalase activity. NO-synthase inhibitors partially abolished the antioxidant effect of CPreC in ischemia.

Conclusion: CPreC had no influence on FRRs in brain tissue in normoxia, but prevented their excessive activation after ischemia, especially in the delayed period. NO-synthase was involved in the CPreC neuroprotection.

Ischemic Preconditioning Efficacy Following Anabolic Steroid Usage: A Clear Difference Between Sedentary and Exercise-Trained Rat Hearts

Previous studies show that anabolic steroids impair innate cardioprotective mechanisms. Here, we investigated the effect of supraphysiological doses of nandrolone on ischemic preconditioning (IPC) as a potent cardioprotective tool against ischemia reperfusion (IR) injury in rat hearts. Male Wistar rats in two experimental settings of sedentary and exercise-trained (60 min/day swimming, 5 days/week, for 8 weeks) were either pretreated with intramuscular injections of arachis oil (Arach, n = 16) as vehicle or nandrolone decanoate (ND, n = 8), 10 mg/kg/week, for 8 weeks. At the end, the hearts were excised and perfused in a Langendorff system. Then, the vehicle-treated hearts subdivided into the IR (30 min of LAD coronary artery occlusion and 120 min reperfusion, n = 8) and IPC (three cycles of 3-min ischemia and 3-min reperfusion before test ischemia, n = 8) groups and nandrolone-treated hearts served as ND + IPC (nandrolone pretreatment before IR and IPC protocols, n = 8) group. Post-ischemic cardiac function and infarct size were assessed. Reperfusion arrhythmias were analyzed using a standard scoring system. In sedentary hearts, ND slightly increased heart-to-body weight ratio and increased baseline cardiac contractile function. In trained hearts, ND markedly increased heart-to-body weight ratio which was also associated with enhanced baseline cardiac function. ND pretreatment enhanced protective effects of IPC in sedentary group; however, abolished these effects in exercise-trained group. The arrhythmia score was not significantly different between nandrolone-treated groups vs. respective preconditioned groups. Our findings show that ND impairs IPC-induced cardioprotection in exercise-trained rat hearts. Cardiac hypertrophy seems to play a crucial role in this response.

A Review of Humoral Factors in Remote Preconditioning of the Heart

A humoral mechanism of cardioprotection by remote ischemic preconditioning (RIP) has been clearly demonstrated in various models of ischemia-reperfusion including upper and lower extremities, liver, and the mesenteric and renal arteries. A wide range of humoral factors for RIP have been proposed including hydrophobic peptides, opioid peptides, adenosine, prostanoids, endovanilloids, endocannabinoids, calcitonin gene-related peptide, leukotrienes, noradrenaline, adrenomedullin, erythropoietin, apolipoprotein, A-I glucagon-like peptide-1, interleukin 10, stromal cell-derived factor 1, and microRNAs. Virtually, all of the components of ischemic preconditioning's signaling pathway such as nitric oxide synthase, protein kinase C, redox signaling, PI3-kinase/Akt, glycogen synthase kinase β, ERK1/2, mitoK_ATP channels, Connexin 43, and STAT were all found to play a role. The signaling pattern also depends on which remote vascular bed was subjected to ischemia and on the time between applying the rip and myocardial ischemia occurs. Because there is convincing evidence for many seemingly diverse humoral components in RIP, the most likely explanation is that the overall mechanism is complex like that seen in ischemic preconditioning where multiple components are both in series and in parallel and interact with each other. Inhibition of any single component in the right circumstance may block the resulting protective effect, and selectively activating that component may trigger the protection. Identifying the humoral factors responsible for RIP might be useful in developing drugs that confer RIP's protection in a more comfortable and reliable manner.

Effects of glucagon-like peptide 1 analogs in combination with insulin on myocardial infarct size in rats with type 2 diabetes mellitus

AIM

To evaluate the effects of glucagon-like peptide-1 analogs (GLP-1a) combined with insulin on myocardial ischemia-reperfusion injury in diabetic rats.

METHODS

Type 2 diabetes mellitus (T2DM) was induced in male Wistar rats with streptozotocin (65 mg/kg) and verified using an oral glucose tolerance test. After anesthesia, the left coronary artery was occluded for 40 min followed by 80 min reperfusion. Blood glucose level was measured during surgery. Rats were randomized into six groups as follows: (1) control rats; (2) insulin (0.1 U/kg) treated rats prior to ischemia; (3) insulin (0.1 U/kg) treated rats at reperfusion; (4) GLP-1a (140 mg/kg) treated rats prior to ischemia; (5) GLP-1a (140 mg/kg) treated rats at reperfusion; and (6) rats treated with GLP-1a (140 mg/kg) prior to ischemia plus insulin (0.1 U/kg) at reperfusion. Myocardial area at risk and infarct size was measured planimetrically using Evans blue and triphenyltetrazolium chloride staining, respectively.

RESULTS

There was no significant difference in the myocardial area at risk among groups. Insulin treatment before ischemia resulted in a significant increase in infarct size (34.7% ± 3.4% vs 18.6% ± 3.1% in the control rats, P < 0.05). Post-ischemic administration of insulin or GLP-1a had no effect on infarct size. However, pre-ischemic administration of GLP-1a reduced infarct size to 12% ± 2.2% (P < 0.05). The maximal infarct size reduction was observed in the group treated with GLP-1a prior to ischemia and insulin at reperfusion (8% ± 1.6%, P < 0.05 vs the control and GLP-1a alone treated groups).

CONCLUSION

GLP-1a pre-administration results in myocardial infarct size reduction in rats with T2DM. These effects are maximal in rats treated with GLP-1a pre-ischemia plus insulin at reperfusion.

Mitochondria "THE" target of myocardial conditioning

Several interventions, such as ischemic preconditioning, remote pre/perconditioning, or postconditioning, are known to decrease lethal myocardial ischemia-reperfusion injury. While several signal transduction pathways become activated by such maneuvers, they all have a common end point, namely, the mitochondria. These organelles represent an essential target of the cardioprotective strategies, and the preservation of mitochondrial function is central for the reduction of ischemia-reperfusion injury. In the present review, we address the role of mitochondria in the different conditioning strategies; in particular, we focus on alterations of mitochondrial function in terms of energy production, formation of reactive oxygen species, opening of the mitochondrial permeability transition pore, and mitochondrial dynamics induced by ischemia-reperfusion.

Hypoxic conditioning in blood vessels and smooth muscle tissues: effects on function, mechanisms, and unknowns

Hypoxic preconditioning, the protective effect of brief, intermittent hypoxic or ischemic episodes on subsequent more severe hypoxic episodes, has been known for 30 yr from studies on cardiac muscle. The concept of hypoxic preconditioning has expanded; excitingly, organs beyond the heart, including the brain, liver, and kidney, also benefit. Preconditioning of vascular and visceral smooth muscles has received less attention despite their obvious importance to health. In addition, there has been no attempt to synthesize the literature in this field. Therefore, in addition to overviewing the current understanding of hypoxic conditioning, in the present review, we consider the role of blood vessels in conditioning and explore evidence for conditioning in other smooth muscles. Where possible, we have distinguished effects on myocytes from other cell types in the visceral organs. We found evidence of a pivotal role for blood vessels in conditioning and for conditioning in other smooth muscle, including the bladder, vascular myocytes, and gastrointestinal tract, and a novel response in the uterus of a hypoxic-induced force increase, which helps maintain contractions during labor. To date, however, there are insufficient data to provide a comprehensive or unifying mechanism for smooth muscles or visceral organs and the effects of conditioning on their function. This also means that no firm conclusions can be drawn as to how differences between smooth muscles in metabolic and contractile activity may contribute to conditioning. Therefore, we have suggested what may be general mechanisms of conditioning occurring in all smooth muscles and tabulated tissue-specific mechanistic findings and suggested ideas for further progress.

Effects of preconditioned plasma collected during the late phase of remote ischaemic preconditioning on ventricular arrhythmias caused by myocardial ischaemia reperfusion in rats

Objective The administration of preconditioned plasma collected during the late phase of preconditioning has been shown to reduce myocardial infarct size. This study aimed to investigate if preconditioned plasma could attenuate ventricular arrhythmias in a rat model in vivo. Methods Eighty rats were randomized to eight groups (10 rats/group). Two groups provided preconditioned or non-preconditioned plasma 48 h after transient limb ischaemia or the control protocol. Six groups of ischaemia-reperfusion (IR) rats received normal saline, non-preconditioned plasma, or preconditioned plasma, respectively, 1 h (groups A1, A2, A3) or 24 h (groups B1, B2, B3) before undergoing myocardial IR. Electrocardiograms were monitored using a BIOPAC system, and the incidence and duration of ventricular tachycardia (VT) and ventricular fibrillation (VF) were analysed. Results No significant differences existed in the incidence and duration of VT or VF among groups A1-A3 or in the incidence and duration of VT among groups B1-B3. However, there was a significantly lower incidence and shorter duration of VF in group B3 rats than in group B1 rats. Conclusion Preconditioned plasma collected during the late phase of preconditioning can reduce the incidence and duration of VF compared with normal saline, suggesting its anti-arrhythmic potential.

Effects of differential-phase remote ischemic preconditioning intervention in laparoscopic partial nephrectomy: A single blinded, randomized controlled trial in a parallel group design

STUDY OBJECTIVE

There are two windows of protection for remote ischemic preconditioning (RIPC), an early (ERIPC) and a late-phase (LRIPC). While ERIPC has been well studied, works on LRIPC are relatively scarce, especially for the kidneys. We aimed to compare the effects of early-phase versus late-phase RIPC in patients with laparoscopic partial nephrectomy (LPN).

DESIGN

A randomized controlled study SETTING: The Second Affiliated Hospital of Anhui Medical University, 1 May 2012 to 30 October 2013 PATIENTS: Sixty-five ASA 1 to 2 patients scheduled for LPN were located randomly to ERIPC group, LRIPC group and CON group (control).

INTERVENTIONS

Three five-minute cycles of right upper limb ischaemia and reperfusion were performed after induction of anesthesia in ERIPC group. Patients in LRIPC group received similar treatment 24h before surgery, while control patients were not subjected to preconditioning.

MEASUREMENTS

Serum neutrophil gelatinase-associated lipocalin (NGAL) and serum cystatin C (CysC) were evaluated before the induction of anesthesia (0h), 2h (2h) and 6h (6h) after surgery. Unilateral glomerular filtration rates (GFR) were assessed before and after surgery to evaluate overall renal function.

MAIN RESULTS

Serum NGAL and CysC were significantly lower in ERIPC and LRIPC groups at 2h post-operation (P<0.001), 6h post-operation (P<0.001). Additionally, The GFR were significantly lower in ERIPC and LRIPC groups than in CON group at the 3rd month after surgery (P=0.019; P<0.001). Moreover, compared to the ERIPC group, concentration of NGAL and CysC in LRIPC group decreased to a greater extent, while GFR and the percentage of decrement was significantly less in the LRIPC group (P=0.016; P<0.001).

CONCLUSIONS

Regardless of early-phase or late-phase intervention, limb remote ischemic preconditioning confers protection on renal ischemia-reperfusion injury in patients with laparoscopic partial nephrectomy, and the late-phase protection is more prominent.

Rat Models of Ventricular Fibrillation Following Acute Myocardial Infarction

A number of animal models have been designed in order to unravel the underlying mechanisms of acute ischemia-induced arrhythmias and to test compounds and interventions for antiarrhythmic therapy. This is important as acute myocardial infarction (AMI) continues to be the major cause of sudden cardiac death, and we are yet to discover safe and effective treatments of the lethal arrhythmias occurring in the acute setting. Animal models therefore continue to be relevant for our understanding and treatment of acute ischemic arrhythmias. This review discusses the applicability of the rat as a model for ventricular arrhythmias occurring during the acute phase of AMI. It provides a description of models developed, advantages and disadvantages of rats, as well as an overview of the most important interventions investigated and the relevance for human pathophysiology.

MicroRNA-29a/b/c targets iNOS and is involved in protective remote ischemic preconditioning in an ischemia-reperfusion rat model of non-alcoholic fatty liver disease

Remote ischemic preconditioning (RIPC) protects against the injury that is incurred by ischemia and reperfusion (IR); however, the role of RIPC in liver IR injury in non-alcoholic fatty liver disease (NAFLD) remains unclear. In this study, a NAFLD rat model was utilized in a series of different surgical procedures and molecular experiments. Rats of the IR group and the RIPC+IR group exhibited more severe injury than NAFLD control rats (in which the liver was prodded following a median-incision laparotomy). The liver condition, measured by serum alanine transaminase and aspartate transaminase levels, of the RIPC+IR group was better than that of the IR group. In addition, alanine transaminase and aspartate transaminase levels were lower in the RIPC+IR group compared with the IR group (P<0.001). Flow cytometry revealed that the cell apoptosis ratio was significantly lower in the RIPC+IR group than in the IR group (P<0.001). Reverse transcription-polymerase chain reaction (RT-qPCR) was used to assess miR-29a/b/c levels, revealing that they were significantly reduced in the RIPC and RIPC+IR groups, but did not vary in the IR group compared with the control group. RT-qPCR also revealed that iNOS mRNA levels were not significantly different among any of the NAFLD groups; however, western blot analysis indicated that iNOS protein levels were increased in the RIPC group and the RIPC+IR group compared with the control and IR groups. A luciferase reporter assay demonstrated that transfection with miR-29a/b/c mimics significantly decreased the luciferase activities of plasmids containing the wild-type iNOS 3'-untranslated region (UTR) (relative fluorescence intensity: 0.47±0.06 for miR-29a, 0.36±0.07 for miR-29b, 0.41±0.04 for miR-29c; P<0.001), whereas the activities of plasmids containing the mutant iNOS 3'-UTR sequence were not markedly affected [relative fluorescence intensity: 0.99±0.08 for miR-29a (P=0.1349), 0.99±0.09 for miR-29b (P=0.1607), 0.97±0.07 for miR-29c (P=0.1824)]. This suggested that miR-29a/b/c downregulates iNOS by directly targeting its 3'-UTR. In summary, the results suggest that RIPC has a protective effect in NAFLD liver IR injury, which may be due to reduced miR-29a/b/c levels in the skeletal muscle, leading to increased iNOS and, therefore, nitric oxide.

Preconditioning with Azadirachta indica ameliorates cardiorenal dysfunction through reduction in oxidative stress and extracellular signal regulated protein kinase signalling

BACKGROUND

Azadirachta indica is widely distributed in Africa, Asia and other tropical parts of the world. A. indica (AI) is traditionally used for the treatment of several conditions including cancer, hypertension, heart diseases and skin disorders. Intestinal ischaemia-reperfusion is a common pathway for many diseases and may lead to multiple organ dysfunction syndrome and death.

OBJECTIVE

In this study, we investigated the ameliorative effects of AI on intestinal ischaemia-reperfusion injury-induced cardiorenal dysfunction.

MATERIALS AND METHODS

Sixty rats were divided into 6 groups; each containing 10. Corn oil was orally administered to group A (control) rats for 7 days without intestinal ischaemia-reperfusion injury. Group B underwent intestinal ischaemia-reperfusion injury (IIRI) without any pre-treatment. Groups C, D, E and F were pre-treated orally for 7 days with 100 mg/kg AI (100 and (200 mg/kg) vitamin C (100 and 200 mg/kg) respectively and thereafter underwent IIRI on the 8th day.

RESULTS

The cardiac and renal hydrogen peroxide increased significantly whereas serum xanthine oxidase and myeloperoxidase levels were significantly elevated (p < 0.05) in IIRI only when compared to the control. The cardiac and renal reduced glutathione, glutathione peroxidase, protein thiol, non-protein thiol and serum nitric oxide (NO) decreased (p < 0.05) significantly following IIRI. Immunohistochemical evaluation of cardiac and renal tissues showed reduced expressions of the extracellular signal regulated kinase (ERK1/2) in rats with IIRI only. However, pre-treatment with A. indica and vitamin C significantly reduced markers of oxidative stress and inflammation together with improvement in antioxidant status. Also, reduced serum NO level was normalised in rats pre-treated with A. indica and vitamin C with concomitant higher expressions of cardiac and renal ERK1/2.

CONCLUSIONS

Together, A. indica and vitamin C prevented IRI-induced cardiorenal dysfunction via reduction in oxidative stress, improvement in antioxidant defence system and increase in the ERK1/2 expressions. Therefore, A. indica can be a useful chemopreventive agent in the prevention and treatment of conditions associated with intestinal ischaemia-reperfusion injury.